Electrigxmotorxdrlven eva evacuated high speed
rotating system for cameras



March 15, 1966 w E BUCK 3,240,137

ELECTRIC-MOTOR-DREVEiN EVACUATED HIGH SPEED ROTATING SYSTEM FOR CAMERASFiled Sept. 29, 1961 5 SheetsSheet 1 IN VEN TOR.

W/LBLYA/PD E. BUCK ATTORNEYS March 15, 1966 w, BUCK 3,240,137

ELEGTRIC-MOTOR-DRIVEN EVACUATED HIGH SPEED ROTATING SYSTEM FOR CAMERASFiled Sept. 29, 1961 3 Sheets-Sheet 2 fie 2.

I NV EN TOR.

W/LLH/PD E. BUCK A TORNEYS March 15, 1966 w BUCK 3,240,137

ELECTRIG-MOTOR-DRIVEN EVACUATED HIGH SPEED ROTATING SYSTEM FOR CAMERASFiled Sept. 29, 1961 3 Sheets-Sheet 5 INV EN TOR.

N \g r fig W/LLARD E. BUCK 3,240,137 ELECTRIC-MOTOR-DRIVEN EVACUATEDHIGH SPEED ROTATING SYSTEM FOR CAMERAS Willard E. Buck, R0. Box 930,Boulder, Colo. Filed Sept. 29, 1961, Ser. No. 141,684 6 Claims. (Cl.95-11) This invention relates to cameras of a type adapted to photographsequencially short-lived events and, more specifically, cameras of theaforementioned type which operate under conditions of negative pressure.

Cameras designed to record photographically a shortlived event by meansof a sequence of pictures fall into two basic types, namely, those inwhich the film is transported past the lens and those in which the filmremains stationary while the image is swept across the surface thereofby a suitable moving reflector such as a rotating mirror. The formertype is generally employed for photographing events which take placeover a sufiicient time interval to permit a relatively slow camera to beused as there is a definite limit beyond which it becomes impractical totransport the film past the lens. Conversely, where higher speeds arerequired, a reflectancetype camera is ordinarily used because iteliminates the film-transport problems. In fact, cameras of the lattertype have been made and used successfully which will take pictures at arate of well over a million frames per second by means of ahelium-driven turbine turning a metal mirror. Cameras capable ofoperation at these ultra-high speeds are not our present concern,however, but rather, those that can be powered by an ordinary electricmotor.

Specifically, a camera designed in accordance with each of theaforementioned two basically different types will be considered. Thefirst is a socalled drum camera in which the film is positioned on theinside cylindrical surface of a hollow metal drum that is rotated past astationary image reflected thereon by a lens system and a non-rotatablereflecting surface. The second is the rotating mirror camera in whichthe image is swept across the stationary film arranged 'arcuately aboutthe axis of rotation of the mirror.

Considerable difficulty has been experienced with the prior art drum androtating mirror cameras in terms of a tremendous loss in efficiency dueto air friction acting upon either the drum or mirror. For example, athirty horsepower motor is required to turn the drum fast enough to movethe film past the lens at one thousand feet per second which is aboutthe upper limit for a film transport camera. Comparable losses inefiiciency are also found in the rotating mirror cameras.

It has now been found in accordance with the teaching of the presentinvention that by turning either the mirror or the drum in a vacuum, thepower requirements of the system can be greatly reduced. In other words,by operating these units at about ten millimeters of mercury or less, itis possible to turn the drum 670 revolutions per second with only aone-third horsepower motor, the latter speed bringing about a filmtransport speed of onethousand feet per second in the particular drumcamera soon to be described in detail. Under these same conditions ofnegative pressure, a mirror can be driven at speeds as high as threethousand revolutions per second with a one-third horsepower motor.

As might be expected, however, operating the rotating system of a cameraat negative pressures of this order involves quite a bit more than justdrawing air from a sealed cavity as there are significant problemsassociated with the design of effective vacuum-tight seals, lubricationof moving parts and the provision of oil-tight seals capable ofpreventing oil from escaping into the evacuited States Patent atedcompartment containing the rotating system. Also, the design offluid-tight shaft seals which will withstand speeds of 15,000 rpm.without becoming overheated due to friction presents certaindifiiculties which must be solved. Furthermore, probably the single mostdifficult problem is the design of a power transfer assembly operativelyinterconnecting either the drum or mirror of the rotating system withthe motor which is capable of multiplying the speed from a minimum ofabout 3 to 1 up to a maximum of nearly 12 to 1 in the case of themirror. Finally, means must be provided for accurately determining thespeed of the rotating system, be it the mirror or the drum.

It is, therefore, the principal object of the present invention toprovide a novel and improved camera operative under conditions ofnegative pressure to photograph sequentially short-lived events.

A second object of the invention herein disclosed is the provision of anelectric-motor-operated vacuum camera that incorporates an improvedshaft seal which is both fluid and air-tight.

Another objective is to provide a novel arrangement for lubricating theannular O-ring seals around the drive shaft in a vacuum camera.

Still another object of the instant invention is to provide a powertransfer assembly especially suited for use in high speed cameras thatis capable of multiplying a motor speed of about 15,000 rpm. up to200,000 rpm. and more for purposes of driving a rotating mirror.

An additional object is the provision of means by which the speed of therotating system is a relatively high-speed vacuum camera of either therotating mirror or drum type may be accurately determined.

Further objects of the invention are to provide a camera of the classdescribed which is compact, versatile, easy to service, inexpensive tooperate, and decorative in appearance.

Other objects will be in part apparent and in part pointed outspecifically hereinafter in connection with the description of thedrawings that follows, and in which:

FIGURE 1 is a diametrical vertical section, portions of which have beenbroken away to conserve space, showing the details of construction of arotating drum-type electricmotor-driven vacuum camera;

FIGURE 2 is a section taken along line 22 of FIG- URE 1 showing thehelical gear arrangement in the power transfer mechanism;

FIGURE 3 is a section taken along line 3-3 of FIG- URE 1 showing thefriction roller arrangement of the power transfer mechanism;

FIGURE 4 is a vertical diametrical section similar to FIGURE 1 and withportions broken away to conserve space showing an alternative form ofthe invention in which the drive mechanism and associated sealing andlubricating systems have been incorporated in a rotating mirror camera;

FIGURE 5 is a fragmentary diametrical section similar to FIGURE 4, butto a slightly reduced scale, showing an alternative form of the ballbearing assembly journalling the end of the mirror shaft;

FIGURE 6 is an end elevation of the bearing assembly of FIGURE 5; and

FIGURE 7 is a fragmentary diametrical section to an enlarged scaleshowing one of the ball bearings and mounting therefor of the assemblyillustrated in FIG- URES 5 and 6.

Referring now to the drawings for a detailed description of the cameraof the present invention, and in particular to FIGURE 1 for thispurpose, it will be seen to include basically a drive unit, a powertransfer mechanism and a rotating system which have been designated in ageneral way by reference numerals 10, 12 and 14, respectively. The powertransfer mechanism 12 provides the operative connection between thedrive unit and the rotating system 14 functioning to multiply the speedof the latter as much as 12 to 1 above that of the motor. Drive unit 10,which has not been shown in detail, comprises merely an electric motor16 of a type available commercially which will produce speeds at itsshaft 18 of the order of 15,000 r.p.m. For purposes of the presentinvention, motor 16 is preferably of the series type which may beoperated at intermediate speeds and which also provides certain magneticbraking features that are useful in slowing down the rotating system atthe end of a run. Fractional horsepowers of the order of one-thirdhorsepower are all that are required of the motor to drive either thedrum 20 or the mirror 22 (FIGURE 4) of the rotating systems illustratedherein provided that these elements are housed in an evacuated cavity.Of course, if the drum of the FIGURE 1 modification or the mirror of thedesign shown in FIGURE 4 were to be made appreciably larger, a slightincrease in horespower in the drive unit would be required.

As has already been mentioned briefly, as much as thirty horsepower in adrive unit is required to operate the rotating system in air at thedesired speeds due to the substantial friction losses; therefore, therotating system must be sealed off from the motor by an effectiveair-tight seal surrounding motor shaft 18. Also, this shaft must be keptwell lubricated in order to insure cool troublefree operation. O-ringseals encircling a shaft the size of motor shaft 18 would fail veryquickly from the heat generated at speeds which could go as high as15,000 r.p.m.; therefore, it is necessary to either reduce the diameterof the terminal end of the motor shaft to a size where relative speedbetween the adjacent contacting surfaces of the O-ring and shaft arematerially less or, preferably, provide the shaft 18 with a hardenedsteel extension 24 as illustrated which includes a section of reduceddiameter 26 that will withstand the substantial torque loads to which itis subjected. In the particular form shown, the shaft extension 24includes a socket 28 at one end sized to receive the terminal end of themotor shaft 18 with a tight fit.

Two small diameter O-ring seals 30 encircle the section of reduceddiameter 26 of the shaft extension 24 forming therewith both an air andfluid-tight seal. These O-ring seals are housed within an annular groove32 bordering a central opening provided in supplementary end plate 34attached to the housing 36 of motor 16. A recess 38 is provided in oneface of the end plate surrounding the central opening therein sized andpositioned to receive the socket-containing portion of the shaftextension.

Lubrication of the O-ring shaft seal is accomplished in a novel way bymeans of a passage 40 opening into annular groove 32 between the O-ringswhich are spaced apart slightly. This passage also opens onto theexterior of the end plate where a grease fitting 42 of the typeincluding a ball check 44 is provided. Thus, a lubricant is forced underpressure into annular groove 32 by means of fill-opening 46 in thegrease fitting 42. The speed at which the section of reduced diameter 26of shaft extension 24 is turning, however, tends to whirl the lubricantcentrifugally back into passages 40; therefore, a positive pressureshould be maintained on the lubricant to continually force it in aroundthe shaft and O-rings. Also, a problem arises in connection withdetermining whether or not the shaft is adequately lubricated when thisshaft seal is not visible.

With the structure of the present invention, these problems are solvedquite simply and easily but in a novel manner. First of all, a lubricantreservoir 48 is located in end plate 34 and connected to receivelubricant from passage 40 by branch passage 50. Reservoir 48 opens ontothe exterior surface of the end plate 34 where it is closed by a plug 52having a control opening 54 therein.

Reservoir 43 is cylindrical and a small piston 56 is mounted therein forreciprocal movement. A compression spring 58 positioned between the plugand piston biases the latter in a direction to eject lubricant from thereservoir into the branch passage and then into the shaft seal thuscontinuously supplying lubricant thereto under pressure whenever asupply thereof is available in the reservoir. In order to determinewhether an adequate reserve supply of lubricant is available in thereservoir, a pin 60 is attached to the piston projecting axiallytherefrom through the central opening 54 in plug 52 within which itreciprocates. Accordingly, when the pin is extended in substantialamount outside the plug indicating that the piston is retracted againstthe compression spring due to an abundance of lubricant in thereservoir, the operator knows the shaft seal is adequately lubricated.If, on the other hand, the pin is retracted, it is an immediateindication that the reservoir may be empty and an additional supply oflubricant is necessary before the unit can be operated.

Reference numeral 62 designates, in a general way, the housing whichencloses the rotating system 14 of the camera. This housing includes, inthe particular form shown, an annular flange 64 projecting from end Wall66 thereof that is attached to endplate 34 and cooperates therewith todefine a chamber 68 in which the power transfer mechanism 12 is located.The joint between the endplate 34 and flange 64 of housing 62 isprovided with an annular air-tight seal provided by O-ring 70. Anopening 71 in flange 64 is provided with a hose fitting 73 that enablesthe air to be pumped from the housing containing the rotating system andalso chamber 68.

Reference will now be made to FIGURES 1, 2 and 3 for a description ofthe power transfer mechanism 12 which functions to multiply the outputspeed of shaft 18 up to the operating speed required of the rotatingsystem. At this point it would, perhaps, be well to mention thattransmissions capable of accomplishing speed multiplication of the orderof 12 to 1 and greater are notoriously old in the art for applicationsin which the ultimate speed to be achieved does not exceed a fewthousand r.p.m.; however, these same prior art transmissions areincapable of producing the speeds that are needed in the cameras of theinstant invention which run as high as 180,000 r.p.m. For example, anordinary spur gear transmission will shear the teeth off the gearsunderload at speeds far less than even the 40,000 r.p.m. at which thedrum type camera of the present invention can operate.

It has now been found, however, that by combining sets of 45 helicalgears and friction rollers the foregoing problems are overcome and atransmission 12 capable of output speeds of 180,000 r.p.m. from a 15,000r.p.m. drive becomes practical. A first 45 helical gear 72 is mounted onthe section of reduced diameter 26 of shaft extension 24 for rotationadjacent endplate 34 in chamber 68. The surface of endplate 34 facingthe interior of chamber 68 is provided with at least three cylindricaldepressions 74 spaced the same radial distance from the axis of rotationof shaft 18 and arranged with their centers in equi-angularly spacedrelation to one another. In the particular form illustrated herein,three such depressions spaced apart angularly 120 are used. There is, ofcourse, a limit on how many depression can be spaced around theperiphery of the first helical gear 72 depending upon the size of thehelical gears 76 that mesh with gear 72 and the diameter of the latter;however, for practical purposes, a set of three helical gears 76 havingteeth oppositely inclined at an angle of 45 to the axis of rotation ofgear 72 perform entirely satisfactorily. Endwall 66 of housing 62likewise, is provided with cylindrical depressions 74 corresponding toeach of the depressions in endplate 34 and located directly oppositesame.

An O-ring 78 is mounted within each cylindrical depression and a rollerbearing 80 is, in turn, mounted within each O-ring. A shaft 82 uponwhich is mounted helical gear 76 is journalledfor rotation within eachof the opposed pairs of roller bearings 80. Each shaft 82 also carries ahardened steel friction roller 84 that has its cylindrical surface infrictional engagement with one end of driven shaft 86 upon which eitherthe drum 20 or mirror 22 (FIGURE 4) are mounted as shown most clearly inFIGURE 3.

Now, in the preferred embodiment of the invention, the center of each ofthe cylindrical depressions 78 is displaced radially toward the axis ofrotation of shaft 18 a few thousandths of an inch rather than beinglocated coincident with the axis of rotation of shaft 82 as determinedby the diameters of helical gears 72 and 76. When so constructed,O-rings '78, being both compressible and resilient, are pre-loaded in adirection to bias both gear 76 and friction roller 84 into forcedcontact with helical gear 72 and shaft 86, respectively. This importantfeature insures the fact that shaft 86 will not become roughened andscored due to slippage between it and the friction rollers.

Certain other advantages of this power tnansfer mechanism are worthy ofbrief mention before proceeding with the description of the remainder ofthe unit. Consider first the gear ratios in the drum-type camera ofFIGURE 1. The motor is seldom run at speeds above 7000 r.p.m. in thistype of camera which means that with approximately a 3:1 ratio betweenhelical gears 72 and 76, shaft 82 will turn only about 20,000 r.p.m.which is well within the range that ball bearings 80 can stand. Even inthe rotating mirror-type of FIGURE 4 where the motor is turned up to itsfull speed of about 15,000 r.p.m., shafts 82 turn only 45,000 r.p.m.with a 3:1 gear ratio which is still well within the capabilities of aball bearing, the main problem being that of lubrication because athigher rotational speeds than these, the shaft tends to whirl thelubricant away centrifugally thus burning out the bearings. The rollers84 in the drum camera hear about a 2:1 ratio to the enlarged end 88 andshaft 86 which means, of course, that the latter shaft will turn thedrum about 40,000 r.p.m. transporting the film close to the maximumspeed of 1000 fps. past the lens. With the mirror system of FIGURE 4,the ratio of the friction rollers to the shaft 86 is nearer 4:1 whichwill turn the mirror 180,000 r.p.m. or 3000 r.p.s. It is for this reasonthat the opposite end of the mirror shaft 86 must also be supported by alike set of friction rollers 84m as shown so that the speed of theroller shafts 90 will be reduced to 45,000 r.p.m. that can be handled bythe ball bearings. Conversely, in the drum-type rotating system ofFIGURE 1 when the maximum drum speed is only about 40,000 r.p.m., theother end 92 of shaft 86 can be journalled directly in a ball bearing 80thus eliminating the necessity for a second set of friction rollers.

In a high speed gear train of the type described herein, the action ofthe helical gears 72 and 76 is also important. High speed loading ofhelical gears tends to shift them axially in opposite directions andsuch thrust components are readily absorbed by the roller bearings 80and the shoulders 94 provided on the ends of the shafts 82 and 90. Theshearing stress on the teeth of the helical gears, on the other hand, isnot a significant factor.

Again with reference to FIGURES 1 and 3, it will be seen that the endwall 66 of the housing 62 for the rotating system 14 has, in theparticular embodiment illustrated herein, a shallow conical surface assurrounding central opening 100 through which shaft 86 passes. Anannular flange 102 with a cylindrical inner surface provides thesidewalls of the housing and is integrally formed as an extension of theendwall. A base 104 is also provided as well as a recessed portion 106adapted to receive the meter (not shown) which indicates the speed ofthe drum.

A generally circular plate 108 is mounted on the annular flange 102 andcontains the centrally-located recess 110 which holds the O-ring 96 andball bearing 80 within which the end 92 of shaft 36 is journalled forrotation.

This plate has an opening 112 adjacent its periphery adapted to receivelens 114 and a second opening 116 designed to receive a film cassette118 of the type shown in my pending application S.N. 740,309, now US.Patent 3,007,384.

Basically, the function of cassette 118 is to transfer a length of filminto the groove 120 provided therefor in the interior of the drum 2t)and rewind same following its exposure. Certain problems arise inconnection with the insertion of the film so that its ends butt properlyand also location of the butted ends so that it can be removed, both ofwhich problems are solved through use of the cassette. A 45 mirror 122is fastened to the plate 108 in position to reflect the image from thelens onto the film.

Shaft 86 includes a section of reduced diameter 124 upon which ismounted a ring magnet 126 of the type having a single localized polearea on its periphery. A hollow plastic ring 123 surrounds the reducedsection of the shaft 86 and is attached to plate 108. Contained withinthis ring is a coil 130 into which signals are induced by the magneteach revolution of the drum. Leads from the magnet pass to an instrumentadapted to indicate the speed of the drum through a suitable rectifiercircuit of conventional design, none of which has been shown.

An annular groove 132 encircles the flange 104 of the housing 62adjacent the open end thereof and carries an Oring 134 which cooperateswith ring 136 to produce an air-tight seal. A step 138 is cut in theinside surface of the ring 136 which mates with a similar step 140defined by the flange 104 and plate 108 to locate these elements inproper assembled relation. The other end of ring 136 is covered by atransparent planar face 142 which is cemented in place and functions toadmit light to the lens 114 and film contained within the drum. A vacuumof the order of 10 mm. Hg or less is drawn by means of a vacuum pumpthrough fitting 74. The O-ring seals 30 and lubricant around the reducedsection 26 of shaft extension 24 seal against the introduction of airfrom the motor side of the unit. O-ring seals 70 and 134 effectivelyseal the remainder of the unit as air is withdrawn from the housing 62containing the rotating system through control opening 100 that looselyreceives the shaft 86. No O-ring seal is necessary between transparentdisk 142 and the edge of ring 136 because the cement and the pressuredifferential tend to seal same.

In operation, the motor is brought up to speed slowly so as to not slipthe friction rollers on the enlarged section of shaft 86. The lens 114is equipped with a shutter (not shown) which remains open for exactlyone complete revolution and is triggered automatically in accordancewith the progress of the short-lived event which is to be photographed.After the photograph has been taken, the magnetic braking effect of theseries electric motor is useful in slowing down the drum. Once the drumhas stopped, the cassette functions to engage a free end of the film andwind it back into the light-tight cannister so it can be removed forprocessing.

The attention is now directed to FIGURE 4 where the system has beenshown adapted for use in a rotating mirror camera. In general, thechanges are minor ones and will only be touched upon briefly. Beforeproceeding, however, it will be well to point out that no attempt hasbeen made in FIGURE 4 to illustrate the entire camera as in the FIGURE 1drum-type, because the film housing, lens system, shutter, etc. of arotating mirror camera are old and well known in the art. It shouldsuffice to point out that the rotating system illustrated hereinfunctions to reflect the short-lived image onto a stationary length offilm arranged arcuately about the mirror in the path of the imagereflected therefrom. Of course, this outer light-tight housing whichholds the film need not be evacuated except for photographicapplications in the ultra-violet range because air resistance is nofactor when nothing but the shutter moves in open air.

The power transfer mechanism 12m has been modified slightly to includelarger diameter friction rollers 84m and eliminating the enlarged end onshaft 86m thus providing a total increase in speed of about 12:1 ratherthan 6:1. Thus, with the motor turning at the full speed of about 15,000rpm. it is possible to realize the 180,000 r.p.m. mirror speed that isrequired for some applications. The substitution of friction rollers 84mand associated shaft 90, ball bearings 80 and O-rings 7 8 on the otherend of the mirror shaft 86m in place of the single ball bearingjournalling the corresponding end of the drum shaft has already beenexplained. The latter elements are positioned within a modified housing14m which includes spaced endplates 66m and 144 interconnected by anintegrally-formed semi-cylindrical sidewall 146. 'A detachable endplate148 cooperates with endwall 144 to define a cavity 150 in which thefriction roller and bearing assembly for one end of the mirror shaft arehoused.

Mirror 22, as shown, has three planar faces and an equilateraltriangular cross section. This mirror is formed integral with its shaft86m. A transparent Window 152 is recessed within the housing 62m for therotating system forming a portion of the sidewall thereof. An O-ringseal 154 surrounds this window and renders the latter vacuum-tight. Inmost instances, it is also desirable to provide an O-rir1g seal 156between endplate 148 and endwall 144.

Finally, with reference to FIGURES 5, 6 and 7 of the drawings, analternative ball bearing assembly for journalling the end of mirrorshaft 86m will be described which can be used as a substitute for thatof FIGURE 4 when the shaft speeds do not exceed a maximum ofapproximately 6000 r.p.s. The friction roller ball bearing assembly ofFIGURE 4 can be used up to speeds of 12,000 r.p.s.; however, it is morecomplex and expensive than that of FIGURES -7, inclusive, which utilizesthe outer race of the ball bearing 80 to replace the friction rollers84m thus eliminating said friction rollers altogether and cutting downthe number of ball bearings required from six to three.

In the particular form shown, housing 146m is modified to eliminateintegral endwall 144 although coverplate 148m is still used but modifiedto eliminate the cavities in the inner face thereof that received theball hearings in the FIGURE 4 embodiment. A bearing support plate 158 isfastened to the inside surface of coverplate 148m and contains threedrilled openings 160 parallel to the axis of mirror shaft 86 and spacedtherefrom a few thousandths of an inch less than the sum of the radii ofsaid mirror shaft and ball bearing 30. As shown, three ball bearings areprovided necessitating three openings 160 angularly spaced 120 from oneanother around the axis of the mirror shaft as a center.

The ball bearings 80 are each mounted on a stub shaft 162 mounted withinthe openings 160. A screw and washer assembly 164 is countersunk intothe face of the bearing support plate 153 and threaded into the outerend of the stub shaft 162, as shown, to secure the latter in place. Anannular shoulder 166 is provided intermediate the ends of the stub shaft162 to provide a step limiting the axial movement of said stub shaftoutwardly under the influence of screw 164. A second screw and washerassembly 168 is provided on the inner race of ball bearing 80 in placebetween it and annular shoulder 166.

As is best shown in FIGURE 7, an annular cavity 170 is provided betweenthe inside cylindrical surface of the inner ball bearing race and theouter cylindrical surface of stub shaft 162 into which a pair of O-rings172 are placed and axially spaced to abut against shoulder 166 and thewasher assembly 168, respectively. Due to the fact that the axis of thestub shaft 162 is slightly closer to the axis of the mirror shaft 86mthan the combined radii of the mirror shaft and ball bearing, asaforementioned, O-rings 172 will be compressed along the portionsthereof between the mirror and stub shafts thus preloading the bearingsinto tight frictional contact with the mirror shaft.

Having thus described the several useful and novel features of thecameras of the present invention in connection with the accompanyingdrawings, it will be apparent that the many worth-while objectives forwhich they were designed have been achieved. Although but two specificembodiments of the invention have been shown and described, I realizethat certain changes and modifications therein may well occur to thoseskilled in the art Within the broad teaching hereof; hence it is myintention that the scope of protection afforded hereby shall be limitedonly insofar as set limitations are expressly set forth in the appendedclaims.

What is claimed is:

1. The motor-driven vacuum camera which comprises: an air-tight housinghaving a transparent portion and a power shaft opening; an exteriorsource of rotational drive power having a drive shaft mounted forrotation within the power shaft opening in the housing; shaft sealingmeans encircling the drive shaft within the powershaft opening in thehousing in liquid and air-tight relation; film-exposure means includinga rotating member located within the housing in position to receive animage from an exterior source through the transparent portion andtransfer the same to a light-senstive emulsion; a driven shaft mountedin the housing in axial alignment with the drive shaft and connected tothe rotating element of the film exposure means; means connected intothe interior of the housing for evacuating same; and, power transfermeans interconnecting the drive and driven shafts forming a drivingconnection therebetween, said means including a first helical gearmounted on the drive shaft inside the housing; a plurality ofradially-displaced shafts journalled for rotation in said housing inequiangularly spaced relation around the common drive and driven shaftaxis at the same radial distance therefrom, a like plurality of secondhelical gears mounted on the radiallydisplaced shafts for rotationtherewith in meshed engagement with the first helical gear, and a likeplurality of friction rollers mounted on said radially-displaced shaftsfor rotation therewith in frictional driving relation to the drivenshaft.

2. The motor-driven vacuum camera as set forth in claim 1 in which: thefirst helical gear has a greater diameter than the second helical gearsand the portion of the driven shaft engaged by the friction rollers.

3. The motor-driven camera as set forth in claim 1 in which: therotating element of the film-exposure means comprises a hollowcylindrical drum adapted to accept a strip of film around the insideperiphery thereof, said drum being attached to the driven shaft forrotation about its center; and in which said film-exposure systemincludes a stationary mirror mounted inside the housing in position toreflect the incoming image onto a film strip inside the drum.

4. The motor-driven vacuum camera as set forth in claim 1 in which: therotating element of the film-exposure means comprises a mirror mountedfor rotation about the driven shaft axis, said mirror being positionedto receive the incoming image and reflect same back out through thetransparent portion of the housing onto a light-sensitive emulsionlocated outside said transparent portion in stationary position.

5. The motor-driven vacuum camera as set forth in claim 1 in which: thepower transfer means includes journals on both ends of eachradially-displaced shaft and compressible resilent means preloading eachjournal inward radially so as to maintain the friction rollers in tightfrictional contact with the driven shaft.

6. The motor-driven vacuum camera as set forth in claim 1 in which: asecond plurality of radially-displaced shafts are journalled forrotation within the housing in equiangularly spaced relation around thedriven shaft at the opposite end thereof, said shafts each having their9 axes parallel to one another and to the driven shaft axis at the sameradial distance therefrom; and in which a second like plurality offriction rollers are mounted on said second set of radially-displacedshafts for rotation there- With, said second set of friction rollersjournalling the opposite end of the driven shaft for rotationtherebetween.

References Cited by the Examiner UNITED STATES PATENTS 1,675,189 6/1928MacIndoe 184-45 2,046,982 7/19 6 Warren 74-606 X 2,513,860 7/1950 Gordon308-203 10 Moir et a1. 74-606 Schmitter 74-606 Taylor 88-16 Nallinger74-572 X Stoffert 184-6 Buck 88-16 Nojima 308-203 McAfee et a1. 184-6 10LEO SMILOW, Primary Examiner. WILLIAM MISIEK, Examiner.

1. THE MOTOR-DRIVEN VACUUM CAMERA WHICH COMPRISES: AN AIR-TIGHT HOUSINGHAVING A TRANSPARENT PORTION AND A POWER SHAFT OPENING; AN EXTERIORSOURCE OF ROTATIONAL DRIVE POWER HAVING A DRIVE SHAFT MOUNTED FORROTATION WITHIN THE POWER SHAFT OPENING IN THE HOUSING; SHAFTSEALINGMEANS ENCIRCLING THE DRIVE SHAFT WITHIN THE POWERSHAFT OPENING IN THEHOUSING IN LIQUID AND AIR-TIGHT RELATION; FILM-EXPOSURE MEANS INCLUDINGA ROTATING MEMBER LOCATED WITHIN THE HOUSING IN POSITION TO RECEIVE ANIMAGE FROM AN EXTERIOR SOURCE THROUGH THE TRANSPARENT PORTION ANDTRANSFER THE SAME TO A LIGHT-SENSITIVE EMULSION; A DRIVEN SHAFT MOUNTEDIN THE HOUSING IN AXIAL ALIGNMENT WITH THE DRIVE SHAFT AND CONNECTED TOTHE ROTATING ELEMENT OF THE FILM EXPOSURE MEANS; MEANS CONNECTED INTOTHE INTERIOR OF THE HOUSING FOR EVACUATING SAME; AND, POWER TRANSFERMEANS INTERCONNECTING THE DRIVE AND DRIVEN SHAFT FORMING A DRIVINGCONNECTION THEREBETWEEN, SAID MEANS INCLUDING A FIRST HELICAL GEARMOUNTED ON THE DRIVE SHAFT INSIDE THE HOUSING; A PLURALITY OFRADIALLY-DISPLACED SHAFTS JOURNALLED FOR ROTATION IN SAID HOUSING INEQUIANGULARLY SPACED RELATION AROUND THE COMMON DRIVE AND DRIVEN SHAFTAXIS AT THE SAME RADIAL DISTANCE THEREFROM, A LIKE PLURALITY OF SECONDHELICAL GEARS MOUNTED ON THE RADIALLY-